This invention relates to a magnetron device, more particularly to coupling means between a magnetron and a unit with which the magnetron is combined.
When combined with a unit such as for example a microwave oven, a magnetron generally produces a microwave output to the unit with high efficiency so that such microwave oven is widely used to heat and defrost foodstuffs.
FIG. 1 is a diagrammatic representation of one example of a prior art magnetron device. As shown, the magnetron device comprises a magnetron tube 1 including a cylindrical anode electrode 1a having radial vanes secured to the inner surface of the anode electrode, a cathode electrode, not shown, concentrically disposed with the anode electrode, a cathode input 1b for supplying operating current to the filament of the cathode electrode, and an output terminal 1c for radiating to the outside the microwave generated in the interaction space defined between the vanes and the cathode electode. A plate 2 for mounting the magnetron tube 1 to a casing of the microwave oven, heat radiating fins 3 for rodiating the heat generated in the anode 1a, and a shield casing 4 for shielding the cathode input 1b are secured to the outside of the cylindrical anode 1a by force fitting or shrink fitting. A seat ring 5a is secured to the upper surface of the magnetron tube 1 for receiving a metal gasket 5 made of brass or stainless steel. A waveguide 6 covers the output terminal or antenna 1c and made up of upper and lower plates 6a and 6b. The lower plate 6b is provided with an opening 6c for passing the output terminal 1c and the lower edge 6d of the opening is urged against the gasket 5. The waveguide 6 is fastened to the supporting plate 2 by bolts 7. Thus, the magnetron tube is suspended by an annular shoulder 2a of the supporting plate 2.
With this construction, however, when the bolts 7 are tightened, a large pressure is applied to the upper end of the magnetron tube by the edge 6d of the opening 6c through the gasket 5. As a consequence, a force shown by arrows tends to disengage the magnetron tube from the supporting plate 2. For this reason, it has been necessary to use a strong force fit or to use some means that can prevent disengagement of the magnetron tube. Moreover, as the opening 6c of the waveguide 6 is positioned close to the output terminal or antenna 1c, a spark 20 tends to occur between these elements as shown by dotted lines, thus decreasing the reliability of the magnetron device.